This invention relates to an acceleration sensitive switch device having particular utility in aircraft instrumentation.
Spring supported masses have long been used in accelerometers and other acceleration sensitive instruments such as those used in aircraft. Similarly, there have been various types of prior art sensing devices developed and used for measuring the deflection or displacement of the mass, either in a continuous fashion or when a preselected acceleration level is reached. Such measurement can be carried out mechanically, electrically, electromechanically, hydroelectrically, or in any other manner that is suitable for the use to which the instrument is put.
In avionics type applications, the acceleration sensitive devices that are used are often switches which are activated when the acceleration exceeds a predetermined level. The acceleration switches are typically connected with the autopilot system of the aircraft in a manner to shut off the autopilot in the event of excessive acceleration in the direction of the pitch axis of the aircraft. Acceleration that exceeds a specified amount thus causes automatic shutoff of the autopilot, and the aircraft is then flown by hand.
The acceleration sensitive switches that are presently available for installation in aircraft and for other uses have not been entirely satisfactory in a number of respects. One problem has been the tendency for such devices to be overly complex and costly. In addition, adjustment of existing switches to a different setting or acceleration level is either not possible or at best difficult and time consuming. Even more importantly with regard to aviation, prior art switches are not capable of being tested effectively prior to each flight in order to determine that they are functioning properly. Therefore, when a malfunction occurs it can only be detected when the aircraft accelerates rapidly during actual flight. This situation is manifestly undesirable, particularly since the reliability of existing devices is lacking somewhat and failures are not uncommon.
At present, it is the usual practice to handle the problem of reliability by providing a number of switch units for each aircraft. The installation of multiple units increases the reliability because it is unlikely that all of the units will fail at the same time. However, even with a multiple unit arrangement, failure of one or all of the switches goes undetected. Significant increases in the cost and complexity are also encountered due to the need for installing several switch units in each aircraft.
It is an important object of the present invention to provide an acceleration sensitive switch device which operates with improved reliability in comparison to existing devices.
Another important object of the invention is to provide a device of the character described that can be quickly and easily tested at any time to determine if it is functioning properly.
An additional object of the invention is to provide, in a device of the character described, a pair of solenoid coils for testing the operability of the switch. The use of solenoid coils to artifically displace the mass of a spring mass system for testing purposes is a unique arrangement which provides effective checking of the switch at any time.
A further important object of the invention is to provide a device of the character described in which the switch mechanisms are improved in reliability and simplified in construction as compared to prior art devices.
Yet another object of the invention is to provide a device of the character described that may be quickly and easily adjusted as to the acceleration lever necessary to trip the switch.
A still further object of the invention is to provide a device of the character described that is simple and economical to construct, install, and maintain.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.